Heretofore, it has been known to provide various immersion heater designs to heat various corrosive liquids in tanks of the type utilized in the plating and semi-conductor industries. Such immersion heaters have generally included a resistance wire with a ceramic insulator assembly disposed in a sheath of material generally resistant to the liquid medium being heated. For a general background of various prior heaters of the immersion type reference may be had, for example, to applicant's aforementioned prior U.S. Pat. No. 4,551,619 and the patents cited therein.
The various problems attendant in prior immersion heaters made from fluoroplastic materials, such as TEFLON or the like, in respect to corrosion resistance and the ability to be economically produced are set forth in applicant's aforementioned application Ser. No. 693,149, U.S. Pat. No. 4,551,619.
Similarly, in applicant's above U.S. Pat. No. 4,551,619 there is disclosed a general background of the problems which occur when heating various types of corrosive liquids in tanks. For example, as used in plating of various articles as well as in preparing articles for plating and similar processes--the liquids being both acid and alkaline, as well as corrosive in many applications.
Accordingly, the present invention provides a new and less costly immersion heater design which consists of small diameter coils of flexible fluoroplastic cable of the general type disclosed and claimed in applicant's aforementioned U.S. Pat. No. 4,551,619. This enables novel heater configurations thereof in conjunction with support frame structures that are of a simple yet rugged construction and which can be economically produced in a variety of configurations, especially for relatively small size plating tanks, as may be utilized in the semi-conductor and metal finishing industries.
For reference to prior type devices utilizing TEFLON type materials in immersion heater applications, reference may be had to U.S. Pat. Nos. 3,657,520, 3,663,779, 4,158,764 and 4,390,776.